The present invention relates to the field of clutch release bearings, in particular for automobile vehicles, of the kind including a manoeuvring member which can be moved in translation by a control member such as a clutch release yoke or the piston of a hydraulic actuator, a thrust bearing adapted to operate on the clutch release mechanism of a clutch, such as a diaphragm spring, and a self-alignment elastic connecting member between the thrust bearing and the manoeuvring member providing an axial connection between the thrust bearing and the manoeuvring member and enabling the thrust bearing to centre itself relative to the diaphragm spring if the axis of the diaphragm spring and the axis of the thrust bearing are not exactly coincident at assembly time. A bearing of the above kind is described in the document FR-A-2 663 702 for example.
The self-alignment elastic connecting member is an elastic sleeve between the bore of the fixed race of the thrust bearing and a cylindrical bearing surface of the manoeuvring member. The sleeve, usually made of an elastomer or an equivalent flexible material, includes within its bore a plurality of ribs projecting in the radial direction relative to the bore and which extend axially across the width of the sleeve. These ribs are slightly inclined and take the form of blades whose free edges bear on the cylindrical bearing surface of the manoeuvring member. The ribs can therefore deform and allow the bearing to move in the radial direction relative to the manoeuvring member for self-alignment with the diaphragm in operation.
The self-alignment connecting elastic member is axially fastened to the fixed race of the thrust bearing by virtue of their complementary shapes, a radial flange or an annular bead at the rear extremity of the self-alignment connecting elastic member, opposite the diaphragm, co-operating with a stepped part of the bore in the race, and an annular groove formed at its front extremity co-operating with a radial rim of complementary shape on the inner race. An annular bead projecting from the free front extremity of the manoeuvring member forms an axial abutment for the axial extremity of the ribs of the sleeve.
The self-alignment elastic connecting member therefore also retains the thrust bearing on the manoeuvring member in the axial direction. In the assembly process, the elastic sleeve is first placed in the fixed race, and the manoeuvring member is inserted into the elastic sleeve by means of an axial movement, combined if necessary with a rotary movement to encourage flexing of the ribs of the sleeve. Slopes or bevels at the rear axial extremity of the ribs of the sleeve encourage the passage of the radial bead.
Although the above type of self-alignment sleeve is satisfactory in most applications, it can nevertheless cause problems if the bore in the inner race has a very short length in the axial direction and has no radial rim directed inwards at its front extremity and/or a stepped part in its bore. In this case, the axial fastening between the fixed race and the elastic sleeve is difficult to achieve, and when the manoeuvring member is fitted to the bearing equipped with the sleeve, unintentional axial movement of said sleeve can occur, leading to incorrect positioning of the sleeve relative to the surrounding members, with harmful consequences for subsequent operation of the release bearing. This problem is aggravated because it is difficult to detect this phenomenon because the elastic sleeve is housed between the bearing and the manoeuvring member.
The present invention aims to solve this problem by proposing a sleeve which retains all of its self-alignment capability but which can be firmly held inside the fixed race, even if the axial dimensions of the fixed race are very small and it does not have any rim directed inwards for locking the sleeve in the axial direction.
The clutch release bearing according to the invention is of the type including a rolling bearing which has a rotating race and a fixed race, and mounted on a manoeuvring member which has a tubular part and a radial flange on which a radial portion of the fixed race bears, and a self-alignment sleeve disposed between the fixed race and the manoeuvring member, the self-alignment sleeve being clamped to a cylindrical bearing surface of the member which supports it, and including a metal armature which has a tubular portion delimited in the radial direction by two circular section surfaces, one of the two surfaces being covered with the elastic material forming self-alignment means, characterized in that the other surface of the metal armature is at least partly covered with the synthetic material forming means for clamping to the member which supports the sleeve, the tubular part of the armature being at the level of the cylindrical bearing surface of the support member of the sleeve. The metal armature ensures that the sleeve is sufficiently rigid.
The self-alignment sleeve can be supported by the manoeuvring member or by the fixed race. In either case, all that is required is for the support member to have a short cylindrical bearing surface. The clamping effect is sufficient to prevent all risk of misalignment and incorrect positioning of the sleeve.
In one embodiment of the invention, the elastic material of the sleeve separating the tubular part of the armature and the support member of the sleeve is thin, for example having a thickness between that of the armature and three times the thickness of the armature.
The armature is advantageously extended by a sealing portion with the rotating race. The armature can be extended at both extremities by a sealing portion with the rotating race.
In one embodiment of the invention, the armature abuts axially against a radial surface of the support member of the sleeve.
The sleeve advantageously includes axial force-fitting ribs on its support member.
The self-alignment sleeve can include an annular bead adapted to form an axial abutment between the fixed race and the manoeuvring member.
The sleeve can include means for filtering vibrations separating the radial flange and the fixed race. The sleeve can include sealing means adapted to cooperate with the periphery of the outer race.
The elastic covering of the sleeve separating the tubular part of the armature and its support member absorbs the spread of dimensions and the relatively large deformations inherent to the process of fabricating components such as the races of the bearing by stamping on a press and heat treatment, whereas direct force-fitting of the armature to the race would require better control of dimensions and a more costly fabrication process if excessive or insufficient clamping were to be avoided in some cases. The proximity of the armature to the support member stiffens this whole area of the sleeve and enables force-fitting with sufficient force to prevent subsequent unintentional demounting of the sleeve. The sleeve is therefore effectively fixed either to the fixed race or to a cylindrical bearing surface of the manoeuvring member.